Vogoo.aiFree Aspect Ratio Calculator
This image aspect ratio calculator turns any pixel width and height into a simplified ratio, or solves the missing side from a ratio and one known dimension. The same aspect ratio calculator doubles as an aspect ratio finder, checker and converter for video — free, instant, no sign-up.
Drop an image above to see how it lands in this ratio — letterboxed, or cropped to fill.
Check an image
Drop an image to read its aspect ratio
The image is read in your browser and never uploaded to a server.
How to use
- 1Choose mode. Pick "Calculate size" to get pixel dimensions from a ratio, or "Calculate ratio" to get the ratio from pixel dimensions.
- 2Enter values. Type the numbers you already have. You can also drop an image and let the checker read its dimensions.
- 3Get results. The missing values update as you type. Copy the result, or copy a link that reopens the same calculation.
Formulas
- Height = (Width × Height ratio) ÷ Width ratio
- Width = (Height × Width ratio) ÷ Height ratio
- Ratio = Width ÷ Height, simplified by their greatest common divisor
What is an aspect ratio?
The one-line definition, plus how to read the two numbers correctly.
An aspect ratio is the proportional relationship between an image or video’s width and its height, written as two numbers separated by a colon, such as 16:9.
Vogoo’s aspect ratio calculator reads the first number as width and the second as height. A 4:5 image is therefore taller than it is wide, and a 16:9 video is wider than it is tall.
Aspect ratio has no unit, so a 1600 × 900 photo and a 16 cm × 9 cm print are both 16:9. That is why this image aspect ratio calculator accepts pixels, inches, centimetres and millimetres alike — width and height just have to use the same one.
Common aspect ratios and their pixel sizes
Every ratio below loads into the aspect ratio calculator above with one click.
Aspect ratio for YouTube, Instagram and TikTok
Platform sizes people search for most, with the exact pixels to enter.
Figures checked against each platform’s own help center on 2026-08-10. Platforms change these without notice — re-check before a large batch.
The aspect ratio formula
How the aspect ratio calculator simplifies a ratio, and how to do the same by hand.
Aspect ratio is calculated by dividing width by height, then simplifying that fraction by the greatest common divisor of the two numbers — which is exactly what the aspect ratio calculator above does on every keystroke.
To calculate aspect ratio by hand, divide the width and the height by their greatest common divisor. For 1920 × 1080 that divisor is 120, which gives 16:9.
Video encoders usually require even dimensions, and many codecs and AI image models expect multiples of 8 or 64. Solved pixel values here are rounded to whole numbers; if your encoder or model needs a specific multiple, round the result up to it before exporting.
Worked example
A client asks for 2:3 at 1080p width. Width 1080 ÷ 2 = 540, and 540 × 3 = 1620. The answer is 1080 × 1620 pixels.
Changing aspect ratio: crop, pad or extend
One source image, three different outcomes — and what each one costs you.
Changing aspect ratio is not resizing. Because the proportion itself changes, something has to give — and there are exactly three ways to handle it.
Crop
Cut away the edges that do not fit. Full resolution is kept, but anything outside the new frame is gone — which is why a 16:9 composition rarely survives a move to 9:16 intact.
Pad
Keep the whole frame and add bars. Nothing is lost, but the bars are baked into the export — and a platform that crops again will crop your bars too.
Extend
Generate new content beyond the original edges so the frame grows instead of shrinking — the only one of the three that adds rather than removes.
The fourth option: generate at the target ratio instead
All three start from an image composed for a different shape. Generating at the target ratio skips that compromise entirely.
Enter a prompt, pick the ratio you just calculated, and the image is composed for that shape from the first pixel. No crop, no bars.
Image to ImageUse an existing picture as a reference and generate at the target ratio. The model composes a fresh image guided by your reference, so expect a new take on the idea rather than a reframed copy.
Calculate the dimensions above, then carry those numbers straight into either generator.
Whichever route you take, work out the target dimensions first — most quality loss comes from upscaling to a size that was never calculated properly.
Aspect ratio calculator FAQ
The questions people ask most about ratios and pixel sizes.
More tools
Got your dimensions? Now make the image.
Take the aspect ratio you just calculated straight into Vogoo’s image and video generators.